Recent evidence indicates that perturbations in the TGFbeta signaling pathway plays a crucial role in the development of surgical pancreatic disease, including pancreatic cancer and pancreatitis. However, the mechanisms of TGFbeta signaling in the human pancreas are largely unknown. This lack of basic information is a major obstacle to rational treatment of human pancreatic diseases, and is reflected in the current empiric, and often ineffective treatment of human exocrine pancreatic cancer and pancreatitis. Recently, we have identified a novel signaling pathway for TGF[3 in the pancreas whereby the obligate second messengers of the TGFbeta signaling pathway, the Smads, activate protein kinase A (PKA) in pancreatic acinar cells. This may represent an important mechanism of crosstalk within the acinar cell. Our preliminary data demonstrates a novel interaction of Smads and the regulatory subunit of PKA within pancreatic acinar cells, and also suggests that PICA may mediate growth inhibitory responses induced by TGFbeta. Therefore we hypothesize that TGF's physiological effects on growth are mediated by Smads and their interactions with the PKA signaling pathway. This research proposal is designed to investigate the molecular basis for the interaction of TGFI3 signaling molecules with the PKA signaling pathway. The experiments will address the hypothesis that Smads3 and 4 directly bind to and activate PKA by a previously unidentified, cAMP-independent mechanism, and will determine interaction domains of Smads 3 and 4 and the regulatory subunit of PKA. In addition, we will investigate the role of PKA in TGFbeta-mediated growth inhibition in pancreatic acinar cells. The proposed research integrates physiological studies with novel molecular strategies, an approach likely to reveal important new insights. The long term goal of this project is to gain a detailed understanding of TGF signaling mechanisms in the pancreas that may be of benefit in the treatment and/or prevention of human pancreatic disease.